Clothes on character deform when posing
Unfortunally there's a bit less Information in your question and - AFAIS - not any object in your uploaded file?
So a real general answer...

If you are starting with parenting, maybe you're looking for Parenting with armatures?
Creating Bones for Rigging in Blender

Maybe the problem is cutting in cloths in ellbow and popliteal?
Then IMHO the better solution is using Cloth physics.
A workaround will be using additional bones for sensitive parts.

You can learn much about using weight paint on different bones, if you import a Make Human character (I'm using collada to import) and study the dependicies...

I hope it helps.